Hitherto known devices for conveying fibers into the spinning rotor substantially consist of a supply duct which is usually oriented tangentially to a fiber opening cylinder and opens either in the immediate proximity of the sliding wall of the spinning rotor, or in the space below a separator designed for separating the fiber supply region from the yarn take-off region of the spinning unit. The latter fiber supply device is the more preferable one because of preventing fibers from wrapping about the final yarn product as it is being withdrawn and, because of better guiding of the fibers onto the sliding wall of spinning rotor.
To avoid an increase of axial force on the yarn, and particularly when using high-speed spinning rotors, the diameters thereof have to be reduced. Since simultaneously the diameter of the cylindrical cover projection is to be shortened, the space for the outlet of the fiber supply duct is also reduced. Should the inner diameter of the fiber supply duct be kept in its desired size, it is necessary to reduce the diameter of a separator stud through which the yarn take-off duct is led, which in turn results in the fibers, especially of long staple, tending to wrap about said separator stud. To such fibers, other fibers adhere, thus producing fiber accumulations, increasing linear yarn weight non-uniformity, or choking the directing gap below the separator, and finally causing yarn breaks.
According to the West-German Published Application (DE-OS) No. 1,940,199, this problem is solved by a radial partition provided in the space between the separator and the front wall of the cylindrical cover projectin. Such a measure, however, gives rise to a resistance to air flow adjacent the outlet of the supply duct where an air whirl is produced while fibers are braked and wrinkle before contacting the slide wall of the spinning rotor. Apart from this, a fan for producing a fiber conveying air flow lays relative high claims on power.
In another apparatus described in British patent specification No. 1,411,878 (corresponding to U.S. Pat. No. 3,952,494), the separator is attached to the cylindrical cover projection by means of a stud eccentrically disposed relative to the axis of said projection. In this embodiment it is necessary to withdraw the yarn through an opening which is axial to the spinning rotor and disposed at the separator side opposite the supply duct outlet, which makes the mounting and the drive of the spinning rotor difficult and expensive. Because of a relatively small diameter of the separator supporting stud, long staple fibers tend to wrap about it and cause disadvantages as hereinabove referred to.
In the spinning unit described in the Czechoslovak Pat. No. 135,732, the spinning rotor interior partly accommodates the cylindrical projection together with the outlet of the fiber supply duct which supports the separator. Through the axis of said separator, which is identical with the spinning rotor axis, there is led the yarn take-off duct passing through a defining stud, which is designed for defining in the vertical direction, a directing gap between the lower separator wall and the front wall of the cylindrical projection in the region of the supply duct outlet and which simultaneously serves for fixing the separator. The geometric center of cross-sectional area of the defining stud is eccentric relative to the take-off duct and the cylindrical projection. The directing gap is defined by the vertically aligned peripheral wall of the defining stud, the outlet of the supply duct forming a conical opening practically on the entire free front wall of the cylindrical projection. This outlet is relatively short and is immediately associated with the fiber opening cylinder. The defining stud is an integral part of the separator and bears on the planar surface of front wall of the cylindrical projection.
A disadvantage of the aforedescribed arrangement is that fibers are caught in a gap between the front wall of the cylindrical projection and the lower wall of the defining stud. Apart from some impreciseness of manufacture, this is also caused because the supply duct has a relatively short outlet which is perpendicular to the front wall of the cylindrical projection whereby the leading ends of long staple fibers get into contact with the sliding wall of the spinning rotor as early as at the instant when their relatively long lengths are still engaged by the opening cylinder. An inner planar section of the peripheral wall of the defining stud directs the fibers immediately onto the spinning rotor. By passing over a sharp edge of transition between said planar section and an outer peripheral wall of said stud, the fibers are braked and tend to wrap about the defining stud since the relationship between the entire periphery of the defining stud and the fiber staple length has not been taken into account.